When attaining endless connection of a conveyor belt having, as core bodies, steel cords, it is necessary for all the embedded steel cords to be stripped across the lengths from both ends of the conveyor belt to prescribed lengths. This work is performed by stripping off an upper covering gum and a lower covering gum individually and removing gum around the steel cords cleanly. Conventionally, such a work has been generally performed manually by using a knife or an electrothermal cutter (see, for example, FIG. 11 in Patent Document 1).
However, such a conventional method requires much person-hour, and has very poor work efficiency, which has been problematic. For example, for a conveyor belt having specifications of 1800 mm for the belt width, φ110 mm×110 for the steel cords, 16 mm for the thickness of the covering gum, 8 mm for the thickness of the lower covering gum, in order for the all the steel cords to be stripped across 4 m length, it takes 16 work hours for 8 persons. Particularly, for a belt having a long distance, since it has increased number of endless areas, it takes still more hours. Since such a work itself is heavy and is a work using a knife or an electrothermal cutter requiring many persons, it is highly dangerous, which has also been problematic. In addition, there has been difficulty that the quality thereof is greatly affected by the unevenness of the sharpness of the knives, the level of skill of the workers or the like.
In order to solve the above problems, in Patent Document 1, for example, a device for ripping gum of a conveyor belt is proposed which includes a cylindrical cutting blade portion and linear cutting blade portions which protrude upward and downward from the cylindrical cutting blade portion; wherein gum around the steel cord is ripped by the cylindrical cutting blade portion, as well as, the upper and lower covering gum is ripped by the linear cutting blade portions. In this technique, a device to which two types of cutting blades are attached is pulled by a winch or the like, and is allowed to proceed in the belt length direction, and gum of the upper and the lower covering and gum around the steel cord is cut off. Specifically, first, a part of the steel cord of the belt is exposed (FIG. 2 in Patent Document 1), and a device composed of a linear cutting blade which longitudinally rips an upper surface covering gum and a lower surface covering gum (signs 8, 9 in FIG. 1 in Patent Document 1), and a cylindrical cutting blade which removes remaining gum around the steel cords (sign 5 in FIG. 1 in Patent Document 1) is attached thereto. Thereafter, gum of the upper and the lower covering and gum around the steel cord is cut off at once by pulling this device by a winch or the like and allowing this device to proceed in the belt length direction (FIG. 8 in Patent Document 1).
As a further modification of the above technique, in Patent Document 2, as a ripper for separating the individual steel cords, a ripper including a cutting blade having a three-blade-structure formed by sandwiching a thin blade having a V-shape at the blade edge portion between double holder blades having a V-shape at the blade edge portions such that this thin blade edge is more protruded than the holder blade edges is proposed; and, as a ripper for stripping gum off around each of the steel cords, a ripper in which a cylindrical cutting blade formed by sandwiching a linear thin blade between double cutting blades having a half-cylindrical shape such that the linear thin blade is protruded in the upward direction thereof and in the downward direction thereof is detachably attached inside double holders which extend to the linear thin blade is proposed.